发动机用灰铸铁的低周疲劳行为  

Low Cycle Fatigue Behavior of Gray Cast Iron Used for Engine

作　　者：袁永立[1] 何国球[1] 樊康乐[1] 刘晓山[1] 朱旻昊[2] 

机构地区：[1]同济大学材料科学与工程学院上海市金属功能材料开发应用重点实验室,上海201804 [2]西南交通大学牵引动力国家重点实验室,成都610031

出　　处：《材料研究学报》2013年第5期469-476,共8页Chinese Journal of Materials Research

基　　金：牵引动力国家重点实验室开放课题TPL1306资助项目~~

摘　　要：研究了发动机缸体用灰铸铁材料在室温、150℃和250℃下的低周疲劳行为。根据对拉伸应力-应变、循环应力-应变和应变-疲劳寿命数据的分析,给出了疲劳参数。结果表明:在高温下灰铸铁的弹性模量、强度降低,延伸率增大;循环应力响应表明,在较小的应变幅下经历初期循环硬化、循环软化、断裂,而在高温和较大应变幅下几乎没有硬化阶段,循环软化至断裂;其室温疲劳寿命最长,150℃最短,250℃居中。微观分析结果表明:疲劳裂纹萌生于片状石墨尖端、夹杂物及孔洞处,沿石墨扩展,夹杂物导致分支裂纹及裂纹偏转,延缓裂纹的扩展;灰铸铁的疲劳断裂方式为沿晶和准解理断裂的复合机制,存在扇形解理面和二次裂纹,解理台阶上观察到疲劳条带和韧窝。Low cycle fatigue （LCF） behaviors of grey cast iron used for cylinder were investigated at room temperature （RT）, 150℃ and 250℃. Tensile stress-strain curves, cyclic stress-strain curves and fa- tigue life curves were obtained. The results show that Young＇ s Modulus, proof strength and ultimate ten- sile strength of grey cast iron decreased with increasing temperature, while the elongation increased. Cyclic hardening/softening exhibited cyclic hardening initially, then softening and fracture at lower strain amplitudes, while it exhibited cyclic softening and fracture directly without cyclic hardening at 150℃, 250℃ and higher strain amplitudes. Fatigue life decreased with the increase of temperature and was lowest at 150℃. LCF cracks initiated predominantly at the flake graphite tip, near-surface defects such as inclusions and voids, and crack would propagate along graphite. Heterogeneous inclusions contributed crack deflection and bifurcation which would decrease the propagating rate. Crack propagation was mainly characterized by fan shaped cleavage plane, secondary cracks, fatigue striation and some dimples, which indicated the fractural mechanism is intergranular and quasi-cleavage cracks.

关 键 词：金属材料 灰铸铁 低周疲劳 循环应力响应 疲劳裂纹 疲劳断裂 

分 类 号：TG251[金属学及工艺—铸造]